Steel for producing machine components formed from solid stock

ABSTRACT

The invention relates to a steel and a processing method for producing machine components formed from solid stock, particularly for vehicle construction, having a primarily bainitic structure, characterized in that the chemical composition thereof has the following contents in weight percent: 0.10%≦C≦0.25%, 0.15%≦Si≦0.40%, 1.00%≦Mn≦1.50%, 1.00%≦Cr≦2.00%, 0.20%≦Ni≦0.40%, 0.05%≦Mo≦0.20%, 0.010%≦Nb≦0.040%, 0.05%≦V≦0.25%, 0.01%≦Al≦0.05%, 0.005%≦N≦0.025%, 0%≦B≦0.0050%, with the remainder being iron and the steel making-related accompanying elements and residual materials.

The invention relates to a steel and to a processing method for the production of solidly formed machine components, particularly for vehicle construction, with a predominantly bainitic structure.

In this connection, it is provided, according to the invention, that the chemical composition has the following contents, in weight percent:

 0.10% ≦ C ≦ 0.25%  0.15% ≦ Si ≦ 0.40%  1.00% ≦ Mn ≦ 1.50%  1.00% ≦ Cr ≦ 2.00%  0.20% ≦ Ni ≦ 0.40%  0.05% ≦ Mo ≦ 0.20% 0.010% ≦ Nb ≦ 0.040%  0.05% ≦ V ≦ 0.25%  0.01% ≦ Al ≦ 0.05% 0.005% ≦ N ≦ 0.025%    0% ≦ B ≦ 0.0050%

whereby the remainder consists of iron and the melting-related accompanying elements and residual substances.

A particularly advantageous composition is given by claim 2, whereby:

 0.10% ≦ C ≦ 0.20%  0.20% ≦ Si ≦ 0.30%  1.00% ≦ Mn ≦ 1.50%  1.50% ≦ Cr ≦ 2.00%  0.20% ≦ Ni ≦ 0.40%  0.05% ≦ Mo ≦ 0.20% 0.020% ≦ Nb ≦ 0.040%  0.05% ≦ V ≦ 0.20%  0.01% ≦ Al ≦ 0.05% 0.005% ≦ N ≦ 0.025%

whereby the remainder consists of iron and the melting-related accompanying elements and residual substances.

A use of this steel, according to the invention, is given in the production of machine components, particularly for vehicle construction, whereby such components, after forging in a die and after accelerated, controlled cooling have a bainitic structure, to a great extent, with precipitates of special carbides and/or nitrides.

In the case of components produced in this manner, according to claim 4, it is provided that the yield strength after accelerated, controlled cooling from the forming heat amounts to above 620 N/mm².

In this connection, the tensile strength after accelerated, controlled cooling from the forming heat is supposed to amount to between 800 N/mm² and 1100 N/mm², according to claim 5.

Preferably, the yield strength ratio after accelerated, controlled cooling from the forming heat amounts to above 70%.

According to claim 7, it is provided that the ultimate elongation after accelerated, controlled cooling from the forming heat amounts to above 10%.

According to claim 8, it is provided that the ultimate constriction after accelerated, controlled cooling from the forming heat amounts to above 40%.

According to claim 9, the notched-bar impact bending value (DVM notch, room temperature) after accelerated, controlled cooling from the forming heat is supposed to amount to above 25 J.

According to claim 10, it is proposed that the impact strength characteristics can be adjusted by means of stepped cooling, at a high cooling velocity, at first, and a holding stage in the bainitic range, or subsequent aging treatment.

According to claim 11, the component is supposed to be suitable for case hardening and carbonitration.

Finally, the mechanical properties both in the rolled pre-material for forging and in the forged components are supposed to be adjusted by means of thermomechanical treatment. 

1. Steel and processing method for the production of solidly formed machine components, particularly for vehicle construction, with a predominantly bainitic structure, wherein its chemical composition has the following contents, in weight percent:  0.10% ≦ C ≦ 0.25%  0.15% ≦ Si ≦ 0.40%  1.00% ≦ Mn ≦ 1.50%  1.00% ≦ Cr ≦ 2.00%  0.20% ≦ Ni ≦ 0.40%  0.05% ≦ Mo ≦ 0.20% 0.010% ≦ Nb ≦ 0.040%  0.05% ≦ V ≦ 0.25%  0.01% ≦ Al ≦ 0.05% 0.005% ≦ N ≦ 0.025%    0% ≦ B ≦ 0.0050%

whereby the remainder consists of iron and the melting-related accompanying elements and residual substances.
 2. Steel according to claim 1, wherein its chemical composition is such that the following applies:  0.10% ≦ C ≦ 0.20%  0.20% ≦ Si ≦ 0.30%  1.00% ≦ Mn ≦ 1.50%  1.50% ≦ Cr ≦ 2.00%  0.20% ≦ Ni ≦ 0.40%  0.05% ≦ Mo ≦ 0.20% 0.020% ≦ Nb ≦ 0.040%  0.05% ≦ V ≦ 0.20%  0.01% ≦ Al ≦ 0.05% 0.005% ≦ N ≦ 0.025%

whereby the remainder consists of iron and the melting-related accompanying elements and residual substances.
 3. Use of a steel according to claim 2 for the production of machine components, particularly for vehicle construction, which components, after forging in a die and after accelerated, controlled cooling, have a bainitic structure, to a great extent, with precipitates of special carbides and/or nitrides.
 4. Component according to claim 3, wherein the yield strength after accelerated, controlled cooling from the forming heat amounts to above 620 N/mm².
 5. Component according to claim 4, wherein the tensile strength after accelerated, controlled cooling from the forming heat amounts to between 800 N/mm² and 1100 N/mm².
 6. Component according to claim 5, wherein the yield strength ratio after accelerated, controlled cooling from the forming heat amounts to above 70%.
 7. Component according to claim 6, wherein the ultimate elongation after accelerated, controlled cooling from the forming heat amounts to above 10%.
 8. Component according to claim 7, wherein the ultimate constriction after accelerated, controlled cooling from the forming heat amounts to above 40%.
 9. Component according to claim 8, wherein the notched-bar impact bending value (DVM notch, room temperature) after accelerated, controlled cooling from the forming heat amounts to above 25 J.
 10. Component according to claim 9, wherein the impact strength characteristics can be adjusted by means of stepped cooling, at a high cooling velocity, at first, and a holding stage in the bainitic range, or subsequent aging treatment.
 11. Component according to claim 10, wherein it is supposed to be suitable for case hardening and carbonitration.
 12. Component according to claim 11, wherein the mechanical properties both in the rolled pre-material and in the forged component can be adjusted by means of thermomechanical treatment. 